Electric fuse



Sept. 13, 1949. E W|| Ox 2,481,893

ELECTRIC FUSE Filed July 29, 1947 fj@ ,2.3m 29 INVEIVTOR Patented Sept.13, 1949 rUNITED .STATES PATENT 'OFFICE ELECTRIC FUSE Edward Wilcox,Timperley, Altrincham, England, 'assignor to Edward Wilcox & Co.,Limited, Wythenshawe, Manchester, England Application July 29, 1947,Serial No. 764,453 In Great Britain February 2, 1944 (Cl. 20G-133) 4Claims.

rSlhis invention has reference to electric fuses of the kind comprisinga fuse bridge or holder provided with 4contacts across which a cartridgefuse is connected, and a :base provided with complemen-tary contactswith which the contacts on the bridge -or holder are' adapted to beengaged Iwhen the latter is inserted into the base.

Hitherto in electric fuses of the kind referred to the contacts on thefuse bridge or holder have been bifurcated and the cartridge fuse hasbeen mounted across .the contacts by inserting the conducting caps onthe ends of the cartridge fuse .between the limbs of the contactsbetween which the cartridge -fuse is tightly gripped when the contactsare inserted into complementary bifurcated or equivalent contacts on thebase.

The object of the invention is to provide in an electric fuse of thekind referred to, improved means of securing the `cartridge fuse betweenthe vcontacts on the bridge or holder and also securing the contacts onthe bridge or holder.

According to the invention, the contacts on the fuse bridge or holder ofan electric fuse of the kind referred to, have associated with themscrewed stems which screw through tapped holes in the contacts and areslidably mounted in abutments on the bridge or holder and the cartridgefuse is inserted between said stems, the screwing up of :one or both ofwhich yclamps the fuse between the stems and also clamps the lcontactsagainst said abutments.

One embodiment of the invention is hereinafter further described withreference to the accompanying drawings whereof Fig. 1 is a `section ofthe base of the fuse,

Fig. 2 is a section of the fuse bridge or holder,

Fig. 3 is an elevation looking on the right hand side of Fig. 1,

Fig. 4 is an elevation looking on the left hand side of Fig. 2,

Fig. 5 is a section on the line V-V in Fig. 1,

Fig. 6 is a section on the line VI-VI in Fig. 2,

Fig. '7 is a perspective view of the two contacts mounted on the base,

Fig. 8 is a perspective View of vone of the contacts mounted on the fusebridge or holder,

Fig. 9 is a section showing the fuse bridge or holder tted in the baseand interlocked therein,

Fig. 10 is a section on the line X-X in Fig. 9, and

Fig. 11 is a fragmentary section of the fuse bridge or holderillustrating a modication of a detail hereinafter more particularlyreferred to.

Referring to the drawings, I2 is the base of the electric fuse and I3 isthe fuse holder both made of insulating material as is usual. The basel2 has mounted on it in recesses I4, Ida, tubular contacts I5, 15aformed with wideslots I6, l6a of width only slightly less than the fullinternal diameter of the contacts, and with narrow slots I'I, Ila asdescribed in British patent specication No. 544,122. The contacts I5,15a are secured on the base by clamping screws I8, 18a and bushes IS,I9a of insulating material which are screwed into the ends of the base.The screws I8, I 8a also serve to clamp the ends of the conductors whichpass through the bushes I9, 19a into the bores 20, 20a of the contactsI5.

The fuse bridge or holder I3 is `formed with sleeves 2l, 2Ia in the.opposing ends of which are seated the enlarged looped ends 22, 22a ofresilient bifurcated contacts 23, 23a. The ends 22, 22a, of .thecontacts 23, 23a are tapped to receive screw threaded tubular stems 24,24a. The screwed stem 24 has nxed on it a sleeve 25 of insulatingmaterial which is freely rotatable and slidable in the sleeve 2I .and isprovided with an operating piece 26 by means of which it and the stemmay be rotated. The screwed stem 24a has xed on it a reel 33 .ofinsulating material which is a free t in the sleeve 2 Ia. The ends 22,22a of the contacts 23, 23a are formed with projections 2l, 21a whichtake into recesses 28, 28a formed in the walls of the .sleeves 21|, 2Iaand the walls of the latter are formed with notches 29, 29a in which thelimbs of the contacts are received, by which means the contacts 23, 23aare located in the ends of the sleeves and restrained against angularmovement other than only sufficient to enable the contacts to align oradjust themselves to any slight inequalities in their setting or thesetting of the contacts I5, I5a on the base I2.

The opposing ends of the screwed stems 24, 24a are concaved orinternally coned to receive the correspondingly convexed, domed or conedconducting caps 30, 30a on the ends of a cartridge fuse 3I which ismounted between the stems.

To mount the cartridge fuse 3l between the stems 24, 24a the stem 24 isslackened back a little, the fuse is interposed between the stems andthe stem 24 is screwed up, whereupon the fuse is centred and clampedbetween the stems in electrical connection with the contacts 23, 23a.Simultaneously, the contact 23a is pressed against its seat in the endof the sleeve 2 Ia and the contact 23 is drawn against its seat in theend of the sleeve 2 I.

The notches 29, 29a, in which the limbs of the contacts 23, 23a arereceived prevent undue spreading of the members of the limbs by thescrewing of the stems 24, 24a into the ends 22, 22a of the contacts.

The cartridge fuse 3l mounted across the contacts 23, 23a on the holderI3 is electrically connected across the contacts I5, I5a on the base I2,and the contacts on the holder and the base are interlocked, by rstentering the forward or free ends 32, 32a of the contacts 23, 23a intothe contacts I5, I5a through the wide slots I6, ISa and then moving theholder longitudinally relatively to the base to carry the limbs of theholder contacts 23, 23a into the narrow slots II, IIa in the basecontacts I5, I5a. Reverse movement of the holder breaks the interlockand allows of the holder being withdrawn from the base.

The ends 32, 32a of the holder contacts 23, 23a are normally of slightlygreater width than the internal diameter of the base contacts I5, I5a sothat when forced through the slots I6, Ilia the ends 32, 32a enter thecontacts I5, I5a with a snap action and the limbs of the contacts 23,23a are also pressed together therein, thus ensuring good electricalcontact between the two sets of contacts. The pressing together of thelimbs of the holder contacts 23, 23a also has the effect of binding theenlarged. rear ends 22, 22a of the contacts on the stems 24, 24a.

Where the cartridge fuse comprises one or more pieces of fuse wirecontained in the fuse cartridge and clamped by the conducting caps 3U,

30a a supply of spare fuse wire may be wound on the reel 33 for use asrequired. The reel 33 also serves as an operating piece for adjustingthe stem 24a in the end 22a of the contact 23a. Alternatively, the stem24a may have xed on it an insulating sleeve 25a furnished with anoperating piece 26a (as shown in Fig. 11) so that either stem may beadjusted to clamp and release the cartridge fuse 3|'.

The holder I3 may have in it a sight hole 34, Fig. 2, tted with a paneof transparent material 35 through which can be seen whether or not acartridge fuse is in position without removing the holder from the base.

In cases where the bridge or holder contacts are not bifurcated or therear ends of the contacts are not looped, such ends of the contacts maybe made with bosses for the formation of the tapped holes for theclamping stems 24, 24a.

ln some cases springs or spring washers may be arranged on the stems 24,24a. between the contacts 23, 23a. and the adjacent sleeves 2I, 2Ia,which springs or spring washers tend to press the contacts towards eachother and are compressed when the contacts are drawn towards the sleevesby the screwing up of the stems. Alternatively,

springs may be arranged in the bores of the sleeves between the outerends of or collars on the stems and plugs screwed into the sleeves, thescrewing up of the plugs causing the springs to force the front ends ofthe stems into yielding engagement with the conducting caps 30, 30a onthe ends of the cartridge fuse 3I. These arrangements provide that afterthe stems 24, 24a have been adjusted a blown cartridge fuse can beremoved and replaced by a fresh one with a snap-action withoutinterfering with the stems.

I claim:

1. A contact bridge member for electric fuses comprising an insulatingholder having axially alined tubular ends and an intermediate connectingportion, two contact members each of approximately U-shape and havingtheir closed ends in the form of an internally screw threaded circularloop, one contact member being disposed against the inner face of eachtubular end of the holder and free for axial movement, and two screwstems, one screw stem being entered into each tubular end of the holderand screwing into the loop of the adjacent contact member and the twostems being adapted to engage the opposing ends of a fuse insertedbetween them alongside the said intermediate connecting portion.

2. A Contact bridge member as claimed in claim 1 in which key means areprovided to restrain the contact members angularly.

3. A contact bridge member as claimed in claim 1 in which the free endsof the contact members are received and spaced in axial slots in therespective tubular ends of the holder.

4. A contact bridge member as claimed in claim 1 in which key means areprovided to restrain the 4contact members angularly and in which thefree ends of the contact members are received in axial slots in therespective tubular ends of the holder.

EDWARD WILCOX.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,180,659 Kratz Apr. 25, 19161,657,799 Kellner Jan. 31, 1928 FOREIGN PATENTS Number Country Date544,122 Great Britain Mar. 27, 1942

